In recent years, development on an interface device incorporated with a projector and a camera has progressed. In such an interface device, an image is projected from a projector on a projected surface, and a position or motion of a hand or fingers of an operator with respect to the projected image is detected by a camera to realize interactive motion. NPL 1 discloses an interface device using a projector and a camera, which is called Everywhere Displays Projector (hereinafter, an ED projector).
There are intensity modulation type and phase modulation type in a modulation method of a projector. Phase modulation type has advantages such that power efficiency is good, as compared with intensity modulation type, it is possible to design a system in which an image is not darkened even in a case where the distance between a projector and a screen increases, and defective pixels of a modulation element do not cause a defect on a screen. However, phase modulation type requires a light source configured to emit coherent light, and superiority on power efficiency may be lost in a case where a natural picture is displayed. Thus, regarding practical realization, phase modulation type may fall behind intensity modulation type.
In a projector of phase modulation type, as illustrated in FIG. 25, a high-order image of a same pattern as a zero-order image is projected in the periphery of zero-order light 102, which is projected on a main area 101 in the center of a projected image 100. In view of the above, in a projector of phase modulation type, a light shielding member configured to shield a high-order image to be projected in an area other than the main area 101 from light is provided in order to remove the high-order image. Further, in a projector of phase modulation type, as illustrated in FIG. 25, the zero-order light 102 is displayed in the vicinity of a center of each area of a normal image. Theoretically, it is possible to remove the zero-order light 102 in an idealistic system in which a DC (Direct Current) component other than an image is not included. However, it is not possible to completely remove the zero-order light 102 in an actual system.
As a method for removing the zero-order light 102 from the projected image 100, there is a method, in which after a process of shifting the zero-order light 102 by an asymmetrical lens system and making luminance of a shifted image uniform is performed, an image in an area 103 (enclosed by a broken line) where the zero-order light 102 is eliminated is used.
As another method for removing the zero-order light 102 from the projected image 100, there is a method, in which zero-order light is dispersed by image processing. FIG. 26 illustrates an example of a projection device using a spatial modulator of phase modulation type. In the projection device illustrated in FIG. 26, laser light emitted from a light source 201 is collimated by a collimator lens 202, and is irradiated on a spatial modulator 203 of phase modulation type as parallel light. Laser light modulated by the spatial modulator 203 is subjected to Fourier transformation by a Fourier transform lens 204, and an image 215 including zero-order light is projected on a reproduction surface 206. Note that the image 215 including zero-order light is an image obtained by performing Fourier transformation with respect to a CGH 211 (CGH: Computer Generated Hologram). In the example illustrated in FIG. 26, a lens pattern 212 of the Fourier transform lens 204 is superimposed on the CGH 211 by a calculator 210. Then, the image 215 including zero-order light is formed on a focal plane 205. However, zero-order light is dispersed by displacement of the focal position of zero-order light from the reproduction surface 206, and an image 216 in which zero-order light is suppressed is displayed on the reproduction surface 206.
Further, both of the following PTL 1 and PTL 2 disclose a method for removing zero-order light from a projected image.
PTL 1 discloses a light modulation device capable of generating modulated light in which zero-order light is removed. The light modulation device in PTL 1 includes a first spatial light modulator configured to modulate a phase of incident light, a shielding member configured to remove zero-order light from modulated light generated by the first spatial light modulator, and a second modulator configured to modulate a polarization state of modulated light in which zero-order light is removed for each of a plurality of areas.
PTL 2 discloses a projection device, in which a diffraction pattern is displayed on a spatial phase modulation element, and image display is performed by diffraction of light to be irradiated on the diffraction pattern. The projection device in PTL 2 includes a spatial modulation element having the number of rows of compartments, which is two times or more of the number of pixel rows of a display image.